Radio Halos of Galaxies from 1 Jul 2013 through 5 Jul 2013

There
were a variety of goals of this workshop, the main scientific ones included
probing the origin and physical conditions in galaxy halos and related science
such as understanding differences between galaxies, the relation of halos to
star formation and to the environment. Thirty-five edge-on galaxies are being
imaged in full polarization and at two frequencies. As this was the first
face-to-face meeting held by the CHANG-ES consortium, a very important part of
the meeting was to ensure good communication between all participants, to
present scientific ideas via more formal talks, as well as discuss more
informally how the enormous volume of data and data processing could proceed
effectively. At the time of the meeting, all data had been acquired, and approximately
25% of the data had been processed. Therefore many details related todata quality were part of the meeting (e.g.
how to include single-dish data, how data could be protected for PhD students,
how to understand the errors, how to separate thermal from non-thermal emission
given our data set, what supplementary data might be needed, etc.). A
preliminary outline of scientific papers and who would be the lead author was
also drawn up.

Several
exciting results were emphasized, some of which were realized and some are in
the process of exploration. An example is the discovery of a strong
double-lobed radio source immediately behind an edge-on galaxy (UGC 10288), an
idea that may open up new possibilities for probing foreground disks and halos
(like a flashlight illuminating a foreground source). This result has led to a
press release https://public.nrao.edu/news/pressreleases/surprising-image-provides-new-tool which was featured on many
websites. The concept is now being followed up more thoroughly as a direct
result of the Lorentz Center@Snellius workshop, since
it was realized that many such sources around other galaxies may be used as
probes of foreground gas and magnetic fields. Moreover, new techniques (such as
rotation measure synthesis) permit the more detailed analysis of such systems.
Another important result is the prevalence of nuclear cores, at least one of
which is varying with time. This science has yet to be fully explored but will
be soon. Our discussion of scientific papers has led, among other things, to
the organization of our 4th paper and the first that will include all galaxies,
namely the results of our low resolution/high sensitivity data, led by Dr. T. Wiegert. This paper is now well-advanced and will also
culminate in the first public data release for CHANG-ES.

Our
group was very impressed with the support (both organizational and financial)
provided by the Lorentz Center and the freedom associated with the workshop
format. The size and venue were excellent. Since it was our first meeting, the
ratio of formal talks to informal discussions was perhaps higher than might be
typical for a Lorentz Center@Snellius workshop, but
this was a necessary first step. Having learned from our experience at Lorentz Center@Snellius, our follow-up meeting, to be held in Kingston,
Canada, in July 2014, will reverse this emphasis and, in addition, will focus
more on new CHANG-ES results. The workshop dinner/cruise was a delight
and helped us to become a cohesive group. While some of us knew each other only
professionally via scientific publications and occasional conferences, the open
communications encouraged by such activity permits scientific ideas to flow as
well.

Kudos
to the Lorentz Center for being so forward-thinking that such a center exists
and is well supported. I would recommend it to others.